1. Field of the Invention
The present invention relates generally to improved methods for completing wells formed in unconsolidated formations, and more particularly, to methods of stimulating fluid production while preventing the migration of sand with produced fluids from such formations.
2. Description of the Prior Art
Oil and gas wells are often completed in unconsolidated formations containing loose or incompetent sands which migrate with produced fluids. The presence of sand particles in the produced fluids is undesirable in that the particles abrade pumping and other producing equipment and generally reduce the fluid production capability of the formations.
Incompetent subterranean formations include those which contain loose sands that are readily entrained by produced fluids and those wherein the particles making up the formations are bonded together with insufficient bond strength to withstand the forces produced by the intermittent production of fluids from the formations. An often used technique for minimizing sand production from such formations has been to produce fluids from the formations at low flow rates whereby the near well stability of sand bridges and the like in the formations is preserved. However, the collapse of such sand bridges often occurs as a result of unintentional high production rates and pressure surging.
Creating fractures in unconsolidated formations allows the formations to be produced with less pressure drawdown as compared to unfractured formations. Less pressure drawdown helps reduce the instability of the formation sand surfaces. However, the forces produced in the unconsolidated formations as a result of the above mentioned intermittent fluid production and shut-in causes sand bridges in the formations to become unstable and collapse.
Heretofore, unconsolidated formations have been treated by creating fractures in the formations and depositing proppant material in the fractures to maintain them in open positions. In addition, the proppant has heretofore been consolidated within the fractures into hard permeable masses to reduce the migration of sands through the fractures with produced fluids. Further, costly gravel packs with sand screens and the like have been installed in wells which serve as filters and assure that sand does not migrate with produced fluids into the well bores. However, since gravel packs, sand screens and the like filter out the sand, the presence of the filtered sand can add to the flow resistance thereby producing additional pressure drawdown which causes the fracture faces and other portions of the formation to break down and consolidated proppant in fractures, gravel packs and the like to be bypassed.
Thus, there is a need for improved methods of completing unconsolidated hydrocarbon producing formations whereby filter devices such as gravel packs and sand screens are not required and sand migration with produced fluids is prevented by other means.